The centrist politician, who will go head to head against Marine Le Pen in the final round of the election on 7 May, said: “I want to put the Le Touquet border deal back on the table. It must be renegotiated, especially the parts that deal with the fate of isolated child migrants.”

The politician previously raised the issue when he was economy minister, suggesting that his country could tear up the treaty if the UK left the EU.

His comments, which then raised the possibility of migrant camps springing up in the UK, were dismissed by other French government ministers.

A Conservative spokesman said: “This just shows that we need the strong and stable leadership of Theresa May, and why voters need to give her the best possible hand to negotiate in Europe.

“We have always been very clear that protecting and enhancing the shared border between the UK and France at Calais is in both the UK and France’s best interests. By contrast Jeremy Corbyn is not strong enough to keep our borders secure.”